Modern dental care facilities usually include multiple operatories and a central vacuum system. Dental aspirator tips are provided at each operatory for disposition in the patient's mouth to remove aerosols, liquids, solid debris and odors. Typical conventional dental vacuum systems have been far from ideal from the standpoint of noise output, vacuum intensity, and flow rate characteristics, as well as efficiency and reliability. Typically, commercially available dental vacuum systems include a water ring or turbine type vacuum pump, usually with a backup pump specified due to the known unreliability of the primary pumps.
In applicant's co-pending application Ser. No. 477,519, filed Mar. 21, 1983, and hereby incorporated in this application by reference, a dental vacuum system is provided that overcomes most of the drawbacks associated with conventional, commercially marketed systems. The system disclosed in that application is characterized by low noise, excellent efficiency and ideal vacuum intensity and flow rate characteristics. The system also has excellent reliability and is easy to install and utilize in a central facility serving a number of dental operatories.
The system disclosed in my prior co-pending application includes a combined vacuum reservoir/separating tank operatively connected to a rotary vane vacuum pump which is in turn driven by a conventional motor. The rotary vane vacuum pump provides an effective vacuum intensity within a desirable range irrespective of the practical number of operatories connected thereto. In addition, the pump may be operated by a small motor, such as a one horsepower electrical motor, yet it can effectively serve the same number of operatories served by a much larger power source in conventional dental vacuum systems. The pump is preferably continuously lubricated utilizing an oil reservoir directly mounted thereon, and the pump and motor are mounted on a common platform in side-by-side relationship. A V-belt can interconnect pulleys of the pump and motor to provide forced transmission therebetween, and elastomeric feet are provided on the platform to facilitate noise control.
The vacuum reservoir/separating tank, which is operatively connected to dental aspirator tips at a plurality of dental operatories, preferably comprises a cylindrical tank with drain valve means, such as a rubber flap valve disposed at the bottom thereof. A support and drain assembly provides ready connection of the vacuum reservoir/separating tank to an external drain. The support and drain assembly includes a cylindrical support having a first end with an interior diameter slightly larger than the exterior diameter of the tank. Cooperating abutment portions on the tank and on the support and drain assembly operatively engage to limit the penetration of the tank into the support and drain assembly. A false bottom is provided in the support and drain assembly immediately below the rubber flap valve, and a drain pipe extends from an opening formed in the center low point of the false bottom through a side wall of the support and drain assembly. The drain pipe is readily connectable to the dental office's external sewer system. The second end of the support and drain assembly supports the vacuum tank on a horizontal surface in a generally upright position.
In my prior application, a conventional vacuum control unit is operatively attached to the reservoir/separation tank.
In accordance with the present invention, a unique multi-function control component replaces the conventional vacuum control unit, and is attached to the rotary vane vacuum pump between the pump and a separation tank generally similar to that described above.
Generally speaking, gases from the dental operatories (mainly air plus scavenged nitrous oxide and oxygen), separated from liquids and solids in the separation tank, flow through the control component of this invention to the rotary vane vacuum pump intake. Air is also permitted to enter the system through a vacuum controller in the control component and flows to the pump intake. The rotary vane vacuum pump, which is the propulsion source for the entire transport system, forces the arriving gases into an exhaust pipe for ultimate discharge to outside air.
The multi-function control component which is the subject of this invention, serves to: (1) control sealed vacuum (vacuum intensity with zero flow occurring) in the system to a preset maximum; (2) clean air that passes into the system through the sealed vacuum controller of the control component; (3) filter gas flow between the separating tank and the rotary vane vacuum pump; (4) detect moisture in the system downstream of the separation tank but upstream of the vacuum pump; (5) indicate the intensity of the system operating vacuum; and (6) seal the vacuum line between the separation tank and the control component when no vacuum is present.
With respect to the first mentioned control function, it is desirable to limit sealed suction of a dental vacuum system to avoid the inconvenience of aspirating tips sticking too tightly to lips, cheeks, tongue, rubber dams, etc. Some vacuum pumps, such as the positive displacement, rotary vane vacuum pump disclosed in my co-pending application and useable in conjunction with this invention, are capable of generating vacuum intensities in excess of 20 inches Hg. This is much higher than the 5 to 7 inches Hg considered appropriate for general dentistry applications. By limiting the sealed suction or vacuum, the control component of this invention allows a smaller motor to be used and protects the pump against overheating. Since motor horsepower requirements are dependent on flow rates and maximum vacuum, it will be appreciated that a pump having a design maximum vacuum intensity of 17 Hg, with no vacuum control, and under zero flow conditions, would exceed this design limit and require excessive motor horsepower. In accordance with this invention, the control component includes a vacuum controller containing a spring loaded valve that allows bypass air to enter the system through the control component if vacuum levels at the controller exceed a preselected maximum. Valve opening vacuum intensity may be set by adjusting a spring loaded nut in a manner which will be understood by those skilled in the art.
With respect to the cleaning function of the control component, environmental air may contain dust and debris which can adversely affect pump and vacuum controller life. A vacuum controller filter prevents these agents from entering the system by filtering bypass air before it reaches the vacuum controller. To accomplish this task, an easily removable, washable and/or replaceable foam filter element is placed over a perforated cylindrical metal backup screen placed around the upper part of the vacuum controller, which itself is located in an upper wall of the control component.
The control component also has a further filtering function made necessary because the flow from the separating tank, while comprised mainly of gases, may also contain small amounts of low density solids and some aerosols. In addition, under abnormal conditions such as tank overflow, the flow may contain liquids and/or large amounts of bubbles and/or foam. By preventing ingestion of liquids, solids, bubbles, and/or foam into the control component and vacuum pump, pump longevity is enhanced. Accordingly, the control component of this invention also includes a main air filter comprising an easily removable, washable and/or replaceable foam filter element which slips over a perforated cylindrical backup screen located in a main housing of the component. Access to the main air filter is made possible by dividing the housing of the control component into upper and lower portions with a suitable resilient sealing ring therebetween.
With respect to the detection function of the control component, it will be appreciated that during an abnormal condition of tank overflow, for example, the quantity of debris may rapidly overcome the capacity of the main air filter described above. It is therefore desirable to have a means of detecting excessive quantities of moisture (liquids, bubbles and/or foam) downstream of the separating tank but upstream of the rotary vane vacuum pump. Accordingly, an intrinsically safe moisture alarm system is also incorporated into the control component. This system is capable of detecting the presence of liquids, bubbles and/or foam in the control component housing assembly. It operates by lowering the electrical resistance between an alarm probe and its stainless steel holder. If, for example, the resistance is lowered to less than 47,000 ohms, after a two second time delay a signal is sent to a moisture alarm circuit board which then shuts down power to the vacuum pump drive motor and illuminates an alarm indicator light.
Regarding the control component indicator function, a vacuum gauge is attached within the main housing assembly for monitoring the system vacuum intensity, in order to assist in the adjustment of the vacuum controller.
Finally, in relation to the control component sealing function, it will be appreciated that when the rotary vane vacuum pump is turned off, stored vacuum existing in the separating tank and vacuum line plumbing will have tendency to rotate the pump in the opposite direction of its normal operation. This applies a vacuum to the pump exhaust side and could lead to the ingress of outside dust and/or debris into the pump from the exhaust line. Additionally, when the control component is opened for filter maintenance, foul odors from the separating tank could flow into the housing and escape into the environment. Therefore, a spring loaded check valve is built into the housing inlet so that when the vacuum pump is turned off, the vacuum intensity on the pump side of the valve decreases, causing the valve to close, thereby preventing the pump from "reverse motoring" and preventing tank odors from flowing into the control component and possibly out into the environment.
Further objects and advantages of the invention will become apparent upon inspection of the drawings and the detailed description of the invention which follows.